A multi air conditioner has been widely used as means for air-conditioning a plurality of spaces in large-scale premises such as a building. In multi air conditioners, each of outdoor units is closely arranged in order to reduce the entire installation area of a plurality of outdoor units. For an outdoor unit of a multi air conditioner, a top-flow structure in which air sucked in from the side of the outdoor unit is blown out from an upper part of the outdoor unit has been frequently adopted so that a required operation can be performed even under such installation environment. A top-flow type outdoor unit includes a heat exchanger provided on side surfaces of the outdoor unit, an air inlet provided on side surfaces of a casing of the outdoor unit so that air is introduced to the heat exchanger, an air outlet provided on an upper surface of the casing of the outdoor unit, a fan for taking in air present on the side of the outdoor unit towards inside of the outdoor unit and discharging air to outside of the outdoor unit from the air outlet, and a fan motor provided between the heat exchanger and the fan to drive the fan. The fan is rotated by transmitting a drive force of the fan motor to a fan boss provided at the center portion of blades (for example, Patent Literature 1).
In the outdoor unit configured in this manner, when a compressor provided in the outdoor unit is operated, a refrigerant is circulated into the heat exchanger, to perform heat exchange between ambient air of the heat exchanger and the refrigerant. When the fan is rotated, air is taken in to the inside of the outdoor unit from the sides of the outdoor unit, and a wind caused at this time is introduced into the heat exchanger, thereby facilitating heat exchange.